One common method for amplifying the sound of a stringed musical instrument having one or more metal strings made by magnetic permeable material uses a magnetic pickup assembly positioned beneath the strings of the musical instrument. Such a magnetic pickup includes one or more signal picking coils wrapped around one or more magnetic permeable metal cores which are themselves magnetic, or which are magnetized by an adjacent permanent magnet. The magnetic field created by this permanent magnet structure does not generate an electric signal inside of the signal picking coil by itself, because the magnetic field flow, flowing through the turns of the signal picking coil, is a constant. As a result of the position of the strings near the magnet structure of the magnetic pickup, a small string area becomes magnetized. This magnetized string area has a size close to the width of the permanent magnet means exposed from the top side of the pickup. The small, magnetized string area radiates its own flow of magnetic field fluxes with an expanded pattern toward the signal picking coil. The flow of magnetic field fluxes passes through the turns of the signal picking coil. When the string does not vibrate this magnetic flow does not create an electric signal inside the signal picking coil. Picking or strumming a string causes the string to vibrate mechanically and the small, magnetized string area vibrates too. This causes an alternative magnetic field flow to pass through the turns of the signal picking coil, which generates an alternative audio electric signal that corresponds to the frequency of the string mechanical vibration. That audio electrical signal measured between the start and end terminals of the signal picking coil are available for further electronic amplification. Based on that conception theory it was found that the only magnetic pickup capable of reproducing the mechanical vibration of a string with maximum accuracy, is the single coil style magnetic pickup. There is one major undesirable disadvantage of the single coil style magnetic pickup—it picks the electromagnetic noise from the surrounding space, where the magnetic pickup is exposed. Electromagnetic noises in the space are generally produced and radiated by power transformers, power diode rectifiers, electric motors etc.
There are a few conventional methods, which use dual coil magnetic pickup assemblies to cancel that undesirable electromagnetic noise. One of these methods is called classic humbucking pickup, which includes two side-by-side positioned identical coils permanently or switchably connected in series or in parallel. Another popular method uses two stacked (one on the top of the other) identical single coil windings permanently or switchable connected in series or in parallel. These two most popular methods, generally cancel the undesirable noise but they also change the musical specter of the generated audio electric signal in one or another way. The frequency response, the phase and harmonic content of the generated audio electric signal are changed too.